Effects of Source Position on the Dh-Type Ii Cme Properties

Abstract

The properties of SOHO/LASCO CMEs are subjected to projection effects. Their dependence on the source position is important to be studied. Our main aim is to study the dependence of CME properties on helio-longitude and latitude using the CMEs associated with type IIs observed by Wind/WAVES spacecraft (Deca-hecta metric type IIs -DH type IIs). These CMEs were identified as a separate population of geo-effective CMEs. We considered the CMEs associated with the Wind/WAVE type IIs observed during the period January 1997 -December 2005. The source locations of these CMEs were identified using their associated GOES X-ray flares and listed online. Using their locations and the cataloged properties of CMEs, we carried out a study on the dependence of CME properties on source location. We studied the above for three groups of CMEs: (i) all CMEs, (ii) halo and non-halo CMEs, and (iii) limb and non-limb CMEs. Major results from this study can be summarized as follows. (i) There is a clear dependence of speed on both the longitude and latitude; while there is an increasing trend with respect to longitude, it is opposite in the case of latitude. Our investigations show that the longitudinal dependence is caused by the projection effect and the latitudinal effect by the solar cycle effect. (ii) In the case of width, the disc centered events are observed with more width than those occurred at higher longitudes, and this result seems to be the same for latitude. (iii) The dependency of speed is confirmed on the angular distance between the sun-center and source location determined using both the longitude and latitude. (iv) There is no dependency found in the case of acceleration. (v) Among all the three groups of CMEs, the speeds of halo CMEs show more dependency on longitude. The speed of non-halo and non-limb CMEs show more dependency on latitude. The above results may be taken into account in correcting the projection effects of geo-effective CMEs.

Characteristics of CMEs associated with solar flares and DH type II radio bursts based on source position

“…In order to see the dependency of CME properties such as width, speed and acceleration based on longitude, we have grouped the events into three categories ( The limb events have speeds ∼1.4 times greater than the speed of disk events. So, the DH CMEs speed near the disk center is less which is similar to the results reported by many authors (Gopalswamy et al 2001b;Burkepile et al 2004;Michalek et al 2005;Vrsnak et al 2007;Shanmugaraju et al 2009). The CMEs associated with DH type II bursts are more energetic than the metric type II-associated CMEs (Lara et al 2003).The main reason for the longitudinal dependence should be the projection effect.…”

“…The arrows in each plot indicate the mean speed of the distribution. The mean and median speed increases from disk to limb Shanmugaraju et al (2009). reported that the CMEs have more speeds at higher longitudes near the limb than the CMEs observed at lower longitudes near disk centre.…”

Characteristics of coronal mass ejection associated with DH type II radio bursts (All and Limb events)

“…1). Here after many authors (Burkepile et al 2004;Michalek et al 2005;Yeh et al 2005;Wen et al 2007;Shanmugaraju et al 2009) pointed out that the projection effect is more important to study the properties of CMEs. The limb events have the minimal projection effect.…”